Sheet-stripping device in printing presses

ABSTRACT

Sheet-stripping device for printing press having means for pneumatically raising the uppermost sheet of a supply stack at a leading edge thereof includes a plurality of strippers disposed between vertically extending and horizontally spaced stop members for the supply stack, the strippers, respectively, comprising a rodlike holder having a free upper end, and a removable cap of elastic material mounted on the free end of the holder, the cap having at least one stripper fin extending toward the supply stack and projecting over the uppermost sheet of the supply stack.

United States Patent Gramlich 51 Jan. 18, 1972 III FOREIGN PATENTS OR APPLICATIONS Crail ..27l/26 X Switzerland Primary Examiner-Joseph Wegbreit Assistant Examiner-Bruce H. Stoner, Jr.

Attorney-Curt M. Avery, Arthur E. Wilfond, Herbert L Lerner and Daniel J. Tick Sheet-stripping device for printing press having means for pneumatically raising the uppermost sheet of a supply stack at a leading edge thereof includes a plurality of strippers disposed between vertically extending and horizontally spaced ABSTRACT stop members for the supply stack, the strippers, respectively,

comprising a rodlike holder having a free upper end, and a removable cap of elastic material mounted on the free end of the holder, the cap having at least one stripper fin extending toward the supply stack and projecting over the uppermost sheet of the supply stack.

8 Claims, 15 Drawing Figures PATENTEQ JAN 1 8 I972 OBI mbwdz Q ON N 3 9m gum $61 456$ $3 m 000E Q m T N ml m m N 2 @7 4 t mmdE 4nd; miwE SYQE SHEET-STRIPPING DEVICE IN PRINTING PRESSES My invention relates to sheet-stripping device in printing presses and, more particularly, to such device which pneumatically raises the uppermost sheet of a supply stack at its leading edge by means of a plurality of strippers disposed between the vertical stop members of the paper supply stack and having elastic stripper fins which project over the leading edge of the supply stack and above the sheet to be removed.

In printing presses with suction devices for raising the uppermost sheet of the supply stack wherein the suckers of the devices seize the leading edge of the sheet, press stoppages are caused by the fact that one or even more sheets remain adhered to the raised sheet and can be fed-with the latter into the press. To eliminate this difficulty, two different measures have been adopted. In one case, blower nozzles have been placed in front of the supply stack for effecting a fanning out of the uppermost sheet from the remaining sheets of the supply stack and, in the other case, the aforementioned strippers have been provided between the forward paper stop members with which the leading edge of the supply stack comes-into contact.

If such strippers are to operate satisfactorily, they must gently and reliably strip off each second sheet, they must be durable, and they must be readily replaceable.

On the one hand, a stripper must obviously grip the sheet gently so that no damage occurs to the leading edge of the sheet even when the paper is relatively thin; but on the other hand, the stripper fin of the stripper must sweep along the leading edge of the raiseduppermost sheet with adequate firmness so as to strip away reliably therefrom any other sheets adhering thereto. A stripper'fin must accordingly be extremely elastic. In spite of its flexibility, however, it must have adequate durability to avoid a sudden press stoppage due to failure or fracture thereof. It is obvious, of course, that there is no way of preventing such stripper fins from gradually wearing out and from requiring replacement. Therefor, a relatively simple means of replacing wom-out stripper fins is of great advantage. Moreover, the exchangeability of the stripper fins is of importance because a stripper fin of specific structure does not work equally efiectively for all paper thicknesses. It is therefore-desirable to have a timesaving means for adapting or adjusting the type of stripper fin tothe variety of paper that is to be worked on. v

A heretofore known stripper is formed of a flat bar having about a 2 to 3 mm. right-angle bend at the upper end thereof, and a second shorter bar that is fastened to the upper end of the first-mentioned bar. A strip of rubber or plastic material is inseparably and consequently nonexchangeably clamped between both bars. The upper end of this strip isbent at right angles away from the angled end of the first mentioned bar, so that an elastic tongue is formed which projects over the stack of printed sheets (Swiss Pat. No. PS 460,060).

With the foregoing and other objects in view, I provide, in accordance with my invention, sheet-stripping device for printing presseshaving means for pneumatically raising the uppermost sheet of a sheet supply stack at a leading edge thereof comprising aplurality of strippers disposed between vertically extending and horizontally spaced stop members for the sheet supply stack, the strippers respectively, comprising a rodlike holder having a free upper end and a removable cap of elastic material mounted on the free-endof the holder, the cap having at least one stripper fin extending toward the supply stack and projecting over the uppermost sheet of the supply stack.

The elastic cap constructed in accordance with my invention is exchangeable very rapidly and effortlessly so that a printer can employ, with little loss of time and relatively low cost, the particular type of stripper fin, which is most suitable,

. with respect to stripping action and careful handling of the sheet edge, for the-type of paper or cardboard being imprinted.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in sheet-stripping device in printing presses, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes 'may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. I is an elevational view of the sheet stripper of my invention, installed in a sheet stacking device for a printing press; 1 1

FIG. 2 is a sectional view of FIG. I taken along the line H- II in the direction of the arrows, and showing a sheet supply stack with the topmostsheet thereof raised by a pneumatic gripper or sucker,

FIG. 3 is a top plan view of FIG. 1.

FIGS. 4A,4B and 4C are front elevational, side and top plan views respectively, of a particular embodiment of the cap This known stripping device is advantageously employable for a relatively great range of paper types and thicknesses, yet is not v equally efficacious for the extremes of paper thicknesses, namely cardboard and tissue. This known device has a particular shortcoming, however, in that after the stripper tongue has become worn, in addition to the elastic strip, the entire holder with the stripper fin firmly fastened thereto, must also be replaced. The replacement of the whole holder and stripper is uneconomical and is burdened with unnecessary costs since only the worn stripper fin really has to be exchanged.

It is accordingly an object of my invention to provide sheetstripping device in printing press which avoids the aforementioned disadvantages of the heretofore known sheet stripping devices of this general type. More specifically, it is an object of my invention to provide such sheet-stripping device which does not necessitate the uneconomical replacement of the entire holder and stripper when only the worn stripping fin needs replacement, but rather simplifies and minimizes the cost of replacing the stripper fin, especially since extensive experiments had led to the surprising realization that no stripper of a particular construction and specific material affords the same optimal stripping results for all types and thicknesses of paper sheets.

of the cap member; and

FIGS. 7A, 7B and 7C are views also corresponding to those of FIGS. 4A, 4B and 4C, respectively, of a further embodiment of the cap member of my invention.

Referring now to the drawing, and first particularly to FIGS. I to 3 thereof, there is shown therein a traverse or crosspiece I on which vertically extending stop members 2 are secured for guiding the leading edge of the sheets in a supply stack 3. Sheet snippets 4 are fastened to the traverse I inthe spaces between adjacent stop members 2 by means of clamping screws 5. Each stripper 4 is formed of a holder 6 and a stripper cap 7. The lower'end of the holder 6, as viewed in FIG. I, for example, is formed with a slot 8 through which the clamping screw 5 extends.

The cap 7 is formed of elastic material, such as rubber or a suitable plastic material, and is formed at the lower end thereof, as viewed in FIG. '2, for example, with a slot-shaped hollow space 9 wherein the upper end 10 of the holder 6 is inserted, each stripper 4 extends into a recess ll of a blower device 12 which is located at the level of the upper sheets I4 of the supply stack 3. The upper end of the stripper cap 7, as viewed in FIG. 2, for example, is provided with a right-angle bent tongue or stripper fin 13 having a free outer end which projects over the leading edge of the supply stack 3 and is located above the uppermost sheet 14.

The spacing between the stripper fin l3 and the respective uppermost sheet 14 of the supply stack 3 can be adjusted by loosening the clamping screw 5 and shifting the entire stripper 4 in vertical direction. This adjustment is also attainable, however, by mutually exchanging stripper caps 7 of varying lengths. In this case, adjusting the level of the holder in the slot 8, is dispensed with. The level adjustment of the stripper fin I3 is generally dependent upon the thickness of the paper sheets being processed.

A suction rod with a plurality of conventional suckers 16 are located above the sheet supply stack 3 so as to raise the respective uppermost sheets from the supply stack 3 at the leading edge thereof, and to further transport it in a conventional manner over the feed table in direction toward the printing mechanism.

FIGS. 4A, 4B and 4C, show elevational, side and plan views, respectively of an embodiment of a stripper cap 7 formed of rubber or plastic material. The underside of the stripper fin 13a is provided with stripper studs 17. The fin 13a proper is exceptionally flexible, being of very thin construction. This kind of stripper cap 7 is suited especially for thicker types of paper, for example, for strong art or coated paper or stiff cardboard. The great flexibility of the stripper fin 13a is necessary to prevent the stifi' material from being torn off by the suckers 16. The roughened or studded undersurface or edge of the stripper fin 13a of FIGS. 4A, 4B and 4C rubs with sufficient vigor along the leading edge of the raised sheet or sheets 14 so that sheets adhering to the uppermost raised sheet are stripped off therefrom and drop back downward on the supply stack 3.

In the elevational, side and plan views of FIGS. 5A, 5B and 5C, respectively, there is shown a stripper cap 7, also made of rubber or plastic material, which has stripper fins 13b formed with parallel notches 18 therein, so that the stripper fin 13b has the appearance of a comb. This type of stripper fin 13b is particularly suited for very thin sheets, suchasairmail tissue or the like. The individual stripper fingers formed between the notches 18 are flexible and cause no damage to the edges of the sheets but nevertheless rub against the leading edge of the thin sheet fed past them and consequently, strip off therefrom any possible adhering sheets, which thereupon drop back onto the supply stack.

FIGS. 6A, 6B and 6C, with views corresponding to those of FIGS. 4A, 4B and 40respectively, show a stripper cap 7 with bristles 19, for example of hair or nylon, inserted at one -end thereof, and serving as a stripper fin. Depending on the type and length of the bristles, this stripper fin can be used for thin or thick types of paper.

In FIGS. 7A, 7B.and 7C, there is shown an attachable cap 7 having a stripper fin 13c formed of a very thin leaf spring 20 bent into a right-angle shape, one of the legs of which is embedded in the elastic material of the cap 7 and extends in the longitudinal direction thereof.

The operation of the aforedescribed stripper device of my invention is as follows: The stripper fin 13 of the stripper 4 is located at such a distance above the leading edge of the supply stack 3 that the respective uppermost sheet 14 raised by the suckers l6 rubs, with the leading edge thereof, along the underside of the elastic stripper fin 13. If a second sheet is suspended from or adheres to the upper sheet held by the suckers 16. by suitably adjusting the stripper, the second sheet is stripped off the sheet 14 that is to be further transported to the printing mechanism, and the second sheet accordingly drops back onto the supply stack 3. If the sheets being processed are very stifi cardboard, a stripper cap 7 with stripper fins as that of FIGS. 4A, 4B and 4C, may be advantageously used therefor. If very thin sheets are to be raised and transported, it is then advantageous to employ, instead, a stripper cap with stripper fins such as those of FIGS. 5, 6 and 7. The exchange of the stripper caps is rapidlyaccomplished by pulling off the previously used stripper cap from the respective holder6 (FIG. 1 for example) and mounting on the latter the new stripper cap that is to be used. Only in exceptional cases is any subsequent vertical adjustment of the entire stripper 4 necessary, in case caps of the same height or length are used. The adjustment is unnecesary if caps of varying length or height are mutually exchanged. This relatively simple method of exchanging the stripper fins offers asurance that for all materials to be processed, i.e., from the thickest cardboard to the most-lightweight airmail tissue paper, optimal protection against entrainment of adhering double sheets is afforded. Moreover, a worn stripper fin is relatively rapidly and inexpensively replaceable by a new stripper fin.

I claim:

1. Sheet-stripping device for printing press having means for pneumatically raising the uppermost sheet of a supply stack at a leading edge thereof comprising a plurality of strippers disposed between vertically extending and horizontally spaced stop members for the supply stack, said strippers, respectively, comprising a rodlike holder havinga free upper end, and a cap of elastic material-formed with a longitudinal .recex wherein said free end of said holder is received, said cap being slidingly removable from said free end of said holder, said cap having at least one stripper fin extending toward the supply stack for projecting over the uppermost sheet of the supply stack.

2. Sheet-stripping device according to claim I, wherein said.

stripper fin is integral with said cap and extends therefrom at a i right is 3. Sheet-stripping device according to claim 2, wherein said stripper fin is fonned with a roughened undersurfaoe.

4. Sheet-stripping device according to claim 2, wherein said stripper fin is formed with stripper studs extending from the undersurface thereof;

5. Sheet-stripping device according to claim 2 wherein said stripper fin has the shape of a comb.

6. Sheet-stripping device according to claim 1, wherein said stripper fin comprises a plurality of elastic bristles secured to said cap and extending at right angles therefrom.

7. Sheet-stripping device according to claim I, whereinsaid stripper fin comprises an elastic fin partially embedded in said cap and having a right-angle bend formed therein.

8. Sheet-stripping device according to claim 1, wherein said cap is formed of material selected from the group, of elastic materials consisting of rubber-and elastic plastic material. 

1. Sheet-stripping device for printing press having means for pneumatically raising the uppermost sheet of a supply stack at a leading edge thereof comprising a plurality of strippers disposed between vertically extending and horizontally spaced stop members for the supply stack, said strippers, respectively, comprising a rodlike holder having a free upper end, and a cap of elastic material formed with a longitudinal recess wherein said free end of said holder is received, said cap being slidingly removable from said free end of said holder, said cap having at least one stripper fin extending toward the supply stack for projecting over the uppermost sheet of the supply stack.
 2. Sheet-stripping device according to claim 1, wherein said stripper fin is integral with said cap and extends therefrom at a right angle.
 3. Sheet-stripping device according to claim 2, wherein said stripper fin is formed with a roughened undersurface.
 4. Sheet-stripping device according to claim 2, wherein said stripper fin is formed with stripper studs extending from the undersurface thereof.
 5. Sheet-stripping device according to claim 2 wherein said stripper fin has the shape of a comb.
 6. Sheet-stripping device according to claim 1, wherein said stripper fin comprises a plurality of elastic bristles secured to said cap and extending at right angles therefrom.
 7. Sheet-stripping device according to claim 1, wherein said stripper fin comprises an elastic fin partially embedded in said cap and having a right-angle bend formed therein.
 8. Sheet-stripping device according to claim 1, wherein said cap is formed of material selected from the group of elastic materials consisting of rubber and elastic plastic material. 